The Effect of Varying Degrees of Radial Meniscal Tears on the Knee Contact Stresses: A Finite Element Analysis

Abstract:

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Knee osteoarthritis (OA) is believed to result from high levels of the contact stresses on the cartilages and menisci after radial meniscal tears but not clearly proved. This research investigated the effect of varying degrees of radial meniscal tears on the peak compressive and shear stresses in the knee joint. An elaborate three-dimensional (3D) knee finite element (FE) model was developed from CT (computerized tomography) and MRI (magnetic resonance imaging) images. This model was used to model varying degrees of radial meniscal tears (involving 0%-90% radial width of the medial meniscus). Two different conditions were compared: a healthy knee joint and a knee joint with meniscal tears. The peak compressive and shear stresses were found in the posterior region of the medial meniscus and the corresponding zone of the cartilage, and they increased with the increasing width of radial tears. After meniscal tear involving 90% radial width, the peak compressive and shear stresses got their highest values. It shows that meniscal tear greater than 40% radial width drastically increases the contact stresses in the knee joint.

Abstract: A 3D finite element model of a human knee was constructed to study the response of
articular tissues to loads applied to the surface of the femur similar to normal and extreme movements of the joint as in sports activities. A solid model of the femoral and tibial cartilages and menisci were built from post mortem MR images of human knee at full extension using the Pro/Engineer software package. The knee kinematics data was registered for this model and successive articular surface positions were obtained as a function of flexion angle. The cartilage and menisci were modeled as nonlinear orthotropic materials and contact elements were used to
compose the contact layer between articular surfaces. The model determined average contact areas and stress values, which were then compared with published experimental results for equivalent boundary conditions. The presence of menisci increased the contact area in the knee joint, thus creating lower contact stresses on the cartilage than those measured experimentally. Validation of results allows the utilization of 3D knee model for determining the contact areas and the contact stress field for diverse bones positions simulating sports activities.

Abstract: To investigate the response of PCL rupture on the biomechanics of cartilage and menisci, the MRI images of normal human knee at various flexion angles(0°,25°,60° and 80°)were developed 1.5T and the intact and PCL deficient knee models were built based on these images. Then three different loads were applied on these models for the finite element simulation to obtain the von Mises equivalent stress of cartilages and menisci and the reaction force among them. Based on the four flexion angles finite element simulation in ANSYS11.0, we drew the conclusions that: (1) the reaction forces and equivalent stresses were sensitive to PCL deficient at 0° and 60° degrees, (2) The reaction force and equivalent stress of the lateral components increased at 0° and 60°, while the medial components increased at 0 degree and decreased at 60 degree after PCL deficient.

Abstract: Anterior cruciate ligament injuries commonly in traffic accident, sports activities and extreme sports. Anterior cruciate ligament reconstruction is a common practice to help the patients restore the knee stability. However, there is no previous comparison study of single bundle reconstruction, double-femoral double-tibial tunnel reconstruction, single-femoral double-tibial tunnel reconstruction, and double-femoral single-tibial tunnel reconstruction with respect to biomechanical characteristics such as rotational stability, force and stress inside the ligament and grafts, stresses inside the soft tissues. In this study, we developed a pair of three-dimensional finite element models of a lower extremity including femur, tibia, fibula, cartilage, meniscus, and four major ligaments at 0°，25°，60° and 80°of knee flexion. Based on the intact models, single bundle reconstruction, double-femoral double-tibial tunnel reconstruction, single-femoral double-tibial tunnel reconstruction, and double-femoral single-tibial tunnel reconstruction models were also developed. Then, the anterior tibial translations, the forces and stresses inside the ACL and ACL replacements, as well as the stresses inside the menisci, femoral and tibial cartilage were predicted under a combined rotatory load of 10Nm valgus moment and 5 Nm internal torque, respectively using finite element analysis. The rotational stability, ligament forces and stresses in the menisci, femoral and tibial cartilage following double bundle augmentation were superior to the other reconstruction techniques, while there is little advantage in ligament stress compared to that of the single bundle reconstruction. We conclude that double-femoral double-tibial tunnel reconstruction may have advantages with regard to biomechanical characteristics such as rotational stability, force inside the ligament and grafts, stresses inside the soft tissues.

Abstract: The paper presents a complex three-dimensional model of the human knee joint, containing bones, ligaments, menisci, tibial and femoral cartilages. To investigate the role of the articular cartilage in the developing of the osteoarthritis, to analyze and simulate the biomechanical behavior of the human knee joint, a finite element analysis was performed. The non-linearities are due to the presence of the contact elements modeled between components surfaces and to the nonlinear properties of the cartilage, applying a load of 800 N and 1500 N, for 0o in flexion. The results show that misalignment (valgus variation) could damage the articular cartilage because they increase the stress magnitude, that progressively produce articular cartilage damage and it enhances the osteoarthritis phenomenon due to mechanical factors. The displacements and the Von Mises stress distributions on the cartilage and menisci for the virtual prototype, considering an angle of 10 degrees for valgus, are presented. The obtained values are comparable with the values obtained by other authors.

Abstract: To investigate the importance of the meniscal non-linear behaviour on knee joint finite element analysis (FEA) study, the aim of this study was to compare linear elastic and nonlinear hyperelastic material models on the pressure distribution of meniscus. For this purpose, a 3D finite element (FE) knee model of a healthy living subject was constructed from magnetic resonance imaging (MRI) to simulate contact pressure under axial compressive loading. Differences in meniscal contact pressures were observed between linear elastic and nonlinear hyperelastic models. These findings emphasize the importance of accounting the nonlinear material behaviour of the menisci in knee joint FEA studies.